Various arrangements have been attempted to provide seals in oil field tubular connections used in drilling and producing oil and gas wells. Tubular members such as drill pipe and drill collars and the like employed in drilling an oil or gas well are provided with what is normally termed a threaded male pin end and a threaded male box end. When the pin and box are threadedly connected together, shoulders on the tubular members adjacent the threads are engaged. Various attempts have been made to seal the threaded connection to prevent fluids circulated through the tubular members during the drilling operation from exerting stress loads at the abutting shoulders and from contacting the threaded connection formed by the tubular members.
The drilling fluid circulated through the drill string during drilling operations is circulated under substantial pressure and any slight leakage from the threaded connection between adjacent tubular members will quickly cause a "washout" at the shouldered connection requiring the removal of the drill string and replacement of the tubular members where the washout occurs.
"Washout" in a drill string is one of the serious problems encountered in drilling oil and gas wells, and the stress build-up in the tool joints due to such hydraulic pressure is another. Although the drill string members are generally made to API standards, the length of the threaded pin end may vary somewhat from one tubular member to the next. Thus, a seal which might function between two specific tubular members may not function if the next tubular member has a slightly different pin end length so that the seal does not properly engage to prevent fluid contact with the shouldered threaded connection formed between adjacent connected tubular members.
Other types of seals presently employed may require major alteration of the threaded tubular members for receiving the seals, or require some type of internal groove arrangement for receiving a seal therein. Where major alterations of threaded members are required, or even where an internal groove is required in at least one of the tubular members forming the threaded connection, substantial expense may be involved, and some difficulty may be encountered in retrofitting existing drill pipe and drill collars to such sealing arrangements. Also, seals in grooves are generally exposed to the interior of the drill string so that they may be readily dislodged by the fluid circulating therethrough under pressure, or may be subjected to dislodgement by operations conducted in the drill string such as wire line operations, logging tools, stimulation and cementing plugs, drop balls and the like.